Ammonia is an abundant and inexpensive nitrogen source that represents an ideal reagent for amine synthesis. Despite its tremendous potential to provide more direct and economical routes to nitrogen-containing molecules, the use of ammonia in transition-metal-catalyzed reactions has only very recently begun to be realized.[1] The copper-or palladium-catalyzed cross-coupling of aryl halides and amines is a well-established and important method for the synthesis of arylamines in both academic and industrial settings, [2] and recent advances in catalyst design have enabled the use of ammonia as a coupling partner to generate primary arylamines. [3][4][5][6][7] Despite the success of these initial reports, a number of serious limitations regarding the scope and utility of metal-catalyzed cross-couplings of aryl halides and ammonia still exist and must be addressed before this method can be considered a viable alternative to more traditional aniline syntheses. In the case of copper, high loadings of metal and ligand are typically required (10-50 mol %) and less reactive but more economically attractive aryl chlorides, [8] or more readily accessible pseudohalides derived from phenols, are poor reaction partners.[3] Limitations regarding the palladium-catalyzed cross-coupling of ammonia [4][5][6][7] include the coupling of electron-rich, sterically unbiased aryl chlorides as well as the selective coupling of ammonia in the presence of additional amine functionality (chemoselectivity).[9] In addition, currently known systems require catalyst loading of 0.5-5 mol % of palladium as well as elevated temperatures (70-120 8C) to maintain reasonable activity for even simple aryl chloride substrates. The slow rate of oxidative addition of electron-rich aryl chlorides, combined with a lower tendency for such species lacking ortho-substitution to undergo reductive elimination [10] from the requisite [L n Pd(Ar)amido] species, can provide a rationale for the difficulties posed by such reaction partners and the elevated reaction temperatures required for catalyst turnover. Herein, we report the preparation of a suitably designed P,N-ligand that addresses several of the above-described challenges in ammonia cross-coupling, including highly chemoselective transformations and the first report of aryl chloride and aryl tosylate coupling with ammonia at room temperature.Recently, we initiated a research program employing P,Nligands as alternatives to more traditional archetypes in C À N coupling reactions. We envisioned that easily prepared and tunable ligands of this type might provide a useful middle ground in Buchwald-Hartwig aminations between strongly chelating bisphosphanes [2a] and biarylmonophosphanes [2b] that feature only weak secondary metal-ligand interactions.We have found L1 (Me-DalPhos) to be a broadly useful ligand for the palladium-catalyzed cross-coupling of aryl chlorides and amines (including ammonia); however, modestly electron-rich substrates lacking ortho-substitution gave very poor results, requiring harsh re...

Reactions of trimethylphosphine or diphosphines with SbCl(3) in the presence of AlCl(3) or Me(3)SiSO(3)CF(3) give ligand stabilized stibenium and stibinidenium cations. The geometry at each antimony center reveals a variety of environments for antimony that describes new bonding and highlights new directions in the chemistry of the pnictogen elements.

Reactions of indigo with a variety of substituted anilines produce the corresponding indigo diimines ("Nindigos") in good yields. Nindigo coordination complexes are subsequently prepared by reactions of the Nindigo ligands with Pd(hfac)(2). In most cases, binuclear complexes are obtained in which the deprotonated Nindigo bridges two Pd(hfac) moieties in the expected bis-bidentate binding mode. When the Nindigo possesses bulky substituents on the imine (mesityl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, etc.), mononuclear Pf(hfac) complexes are obtained in which the Nindigo core has isomerized from a trans- to a cis-alkene; in these structures, the palladium is bound to the cis-Nindigo ligand at the two indole nitrogen atoms; the remaining proton is bound between the imine nitrogen atoms. The palladium complexes possess intense electronic absorption bands [near 920 nm for the binuclear complexes and 820 nm for the mononuclear cis-Nindigo complexes; extinction coefficients are (1.0-2.0) × 10(4) M(-1) cm(-1)] that are ligand-centered (π-π*) transitions. Cyclic voltammetry investigations reveal multiple redox events that are also ligand-centered in origin. All of the palladium complexes can be reversibly oxidized in two sequential one-electron steps; the binuclear complexes are reduced in a two-electron process whose reversibility depends on the Nindigo ligand substituent; the mononuclear palladium species show two one-electron reductions, only the first of which is quasi-reversible.

Ammonia is an abundant and inexpensive nitrogen source that represents an ideal reagent for amine synthesis. Despite its tremendous potential to provide more direct and economical routes to nitrogen-containing molecules, the use of ammonia in transition-metal-catalyzed reactions has only very recently begun to be realized. [1] The copper-or palladium-catalyzed cross-coupling of aryl halides and amines is a well-established and important method for the synthesis of arylamines in both academic and industrial settings, [2] and recent advances in catalyst design have enabled the use of ammonia as a coupling partner to generate primary arylamines. [3][4][5][6][7] Despite the success of these initial reports, a number of serious limitations regarding the scope and utility of metal-catalyzed cross-couplings of aryl halides and ammonia still exist and must be addressed before this method can be considered a viable alternative to more traditional aniline syntheses. In the case of copper, high loadings of metal and ligand are typically required (10-50 mol %) and less reactive but more economically attractive aryl chlorides, [8] or more readily accessible pseudohalides derived from phenols, are poor reaction partners. [3] Limitations regarding the palladium-catalyzed cross-coupling of ammonia [4][5][6][7] include the coupling of electron-rich, sterically unbiased aryl chlorides as well as the selective coupling of ammonia in the presence of additional amine functionality (chemoselectivity). [9] In addition, currently known systems require catalyst loading of 0.5-5 mol % of palladium as well as elevated temperatures (70-120 8C) to maintain reasonable activity for even simple aryl chloride substrates. The slow rate of oxidative addition of electron-rich aryl chlorides, combined with a lower tendency for such species lacking ortho-substitution to undergo reductive elimination [10] from the requisite [L n Pd(Ar)amido] species, can provide a rationale for the difficulties posed by such reaction partners and the elevated reaction temperatures required for catalyst turnover. Herein, we report the preparation of a suitably designed P,N-ligand that addresses several of the above-described challenges in ammonia cross-coupling, including highly chemoselective transformations and the first report of aryl chloride and aryl tosylate coupling with ammonia at room temperature.Recently, we initiated a research program employing P,Nligands as alternatives to more traditional archetypes in C À N coupling reactions. We envisioned that easily prepared and tunable ligands of this type might provide a useful middle ground in Buchwald-Hartwig aminations between strongly chelating bisphosphanes [2a] and biarylmonophosphanes [2b] that feature only weak secondary metal-ligand interactions. We have found L1 (Me-DalPhos) to be a broadly useful ligand for the palladium-catalyzed cross-coupling of aryl chlorides and amines (including ammonia); however, modestly electron-rich substrates lacking ortho-substitution gave very poor results, requiring harsh...

A palladium-catalyzed intermolecular cross-coupling of two aryl iodides is reported, giving polycyclic ring systems with a high level of convergence and efficiency.

While the utility of vinylogous enolates is well established in the setting of vinylogous aldol, Mannich, and Michael chemistries, literature reports concerning γ-reactivity are scarce for other reaction classes. Presented herein is an unprecedented example of vinylogous reactivity exemplified by the rhodium-catalyzed asymmetric ring-opening reaction of oxabicycles. This strategy also provides a powerful route to incorporate the biologically useful coumarin motif into the hydronapthalene scaffold.

A palladium‐catalyzed intermolecular cross‐coupling of two aryl iodides is reported, giving polycyclic ring systems with a high level of convergence and efficiency.

While anthrones exist as privileged scaffolds in bioactive molecules, the enantioselective functionalization of anthrones is surprisingly scarce in the literature, with no asymmetric transition metal catalyzed example to date. Herein, we report the first asymmetric transition metal catalyzed benzylic functionalization of anthrones through the rhodium(I) catalyzed desymmetrization of oxabicycles. As previously developed rhodium(I) systems were found to be unsuitable for this substrate, a new robust fourth-generation [Rh(cod)OH]2 based catalytic system was developed to address synthetic challenges in this protocol.